(a) Field of the Invention
The present invention relates to a journal bearing for a rotating machine, and more particularly, to an air foil bearing assembly that supports a load of a rotating body as pressure is formed by introducing air, which is a fluid having viscosity between the rotating body and a foil.
(b) Description of the Related Art
Generally, a bearing is a mechanical element that fixes a rotary shaft of a rotating machine at a predetermined position and rotatably supports the shaft while supporting a shaft weight and a load applied to the shaft. In particular, an air foil bearing is a bearing which supports the load by introducing air, which is a fluid having viscosity, between a rotor and the foil which is in contact with a bearing disk by high-speed rotation of the rotor (or rotary shaft) to generate a pressure. Among the air foil bearings, an air foil journal bearing is a bearing that is configured to support a radial load in a vertical direction.
The air foil journal bearing typically has a bump foil disposed along a hollow circumference of a bearing housing and a top foil disposed within the bump foil. The rotor (or rotary shaft) is disposed within the top foil. The rotor rotates while the outer peripheral surface of the rotor and the inner peripheral surface of the top foil are spaced apart.
The bump foil and the top foil form a combining portion (e.g., joint portion) in which a circumferential end portion is bent radially outward. The combining portion is coupled to a slot formed along an axial direction on the inner circumferential surface of the bearing housing. The combining portion allows the bump foil and the top foil to be fixed to the bearing housing without being rotated or pushed in the circumferential direction when the rotor is rotated. The slot of the bearing housing to which the combining portions of the bump foil and the top foil are engaged is formed to have both axial front and rear sides closed to prevent axial disengagement of the bump foil and the top foil.
Therefore, to assemble the bump foil and the top foil to the bearing housing, the bump foil and the top foil are rolled in the circumferential direction and axially inserted into a hollow (e.g., cavity) of the bearing housing, and then the combining portions of the bump foil and the top foil are engaged to the slot in the radial direction of the hollow. By coupling the combining portions of the bump foil and the top foil to the slot in which both axial front and rear sides are closed, the bump foil and the top foil may be fixed to the bearing housing without being diverted to both axial front and rear sides while the rotary shaft is driven.
However, in the related art, it is difficult to form the slot in which both axial front and rear sides are closed in an inner circumference surface of the bearing housing. In addition, the combining portions of the bump foil and the top foil must be combined to the slot inside the hollow of the bearing housing by rolling the bump foil and the top foil in a circumferential direction, therefore it is difficult to assemble the bump foil and the top foil to the bearing housing, and assembly time may be increased. In addition, in the related art, the front and rear assembly directions of the bump foil and the top foil may be switched depending on the skill of an operator, and the bearing housing may be assembled to the rotary shaft to switch the front and rear assembly directions since the front and rear assembly surfaces are symmetrical.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.